INDICATOR

Abstract: An indicator which is useful as a speedometer of a car. A driving internal device (2) is fitted to a printed circuit board (1), and a rotary shaft (6) comprising a hollow shaft is supported by shaft support portions (4, 5) of this driving internal device (2). A pointer (9) is fitted to this rotary shaft (6) and is rotated by the driving internal device (2) through the rotary shaft (6). A light emission diode (12) is disposed inside the rotary shaft (6) and is fixed to the printed circuit board (1). Rays of light of the light emission diode (12) are received by a light reception surface (9a) of the pointer (9) and are then reflected by a reflection surface (9b), so that the pointer (9) emits the rays of light.

Description: TECHNICAL FIELD The present invention relates to an indicating instrument in which a pointer rotated by a internal driving unit indicates a value to be read, and especially to an indicating instrument having a pointer illuminated by a light emitted from an outside light source. BACKGROUND ART Conventional indicating instruments for vehicles such as speedometers which have illuminated pointers are shown in Japanese Utility Model Application Laid Open No. Hei 3-36920 and Japanese Utility Model Application Laid Open No. Sho 54-44545. The first, a conventional indicating instrument disclosed in Japanese Utility Model Application No. Hei 3-36920, has a pointer which includes therein a light source rotated by a rotating shaft. The second, a conventional indicating instrument disclosed in Japanese Utility Model Application Sho 54-44545, has a light source disposed outside a pointer and an offset shaft formed to surround the light source and rotate the pointer. In the first conventional instrument, since electric power must be supplied from a statinary portion to the light source rotating together with the pointer, the structure becomes compicated, thereby causing an increase in axial size of the instrument. In the second conventional instrument, a special shaft such as an offset shaft must be employed and, moreover, the efficiency of the light transmission from the light source to the pointer is low since the light leaks outside the pointer. A similar conventional illuminated pointer structure of the kind mentioned just before is known from US-patent 5,142,456. German Offenlegungsschrift 41 29 057 discloses a pointer with light conducting properties rotatable by a driving unit via a rotating shaft and carrying, rotatable therewith, light sources to which electrical energy is transferred by a transformer arrangement coaxial with the rotating shaft and having a stationary part fastened to a base. Of course, the rotatable part of the transformer system contributes to the mass of the movable pointer unit as do the light sources. European patent application, publication number 0 503 400 discloses an illuminated pointer system with a pointer having light conductive properties, whereby the pointer is rotated by a driving unit via a shaft. The pointer is provided with an angular groove concentric to the shaft and formed in a surface of a pointer hub, such groove serving for housing a light source which is fastened to a base facing said surface of the hub provided with said groove. Light emitted from the light source is reflected from reflecting surfaces of the pointer into light conducting sections of said pointer for illumination thereof. The present invention is made in view of the above, and has an object of providing an indicating instrument in which a light source may be secured to a stationary base member to illuminate the pointer, where the instrument is simple in structure, axially compact, free from the need of a special shaft like an offset shaft, and which achieves a high efficiency in light transmission from the light source to the pointer. The above object, in accordance with the present invention, is achieved by the features of claim 1. Since the light source is secured to the stationary base member, power is supplied through the base member without difficulty so that a simple, axially compact indicating instrument which is free from the need to use a special shaft like an offset shaft may be provided. Further, since the light source is disposed in an accomodation space which is formed inside either one of or both the bearing and the rotating shaft, the light source is enclosed by either one or both the bearing and the rotating shaft so that the light coming from the light source may be transmitted to the pointer without leaking out and the efficiency of the instrument's light transmission is enhanced. An indicating instrument according to the present inven tion is further characterized in that a light collecting portion having a light collecting surface which faces the light source and reflecting surface which couples with the light collecting surface is formed at the foot portion of the pointer approximately perpendicular thereto, and the collecting surface is formed in a curved shape to condence the light onto the reflecting surface. As a result, since the curved light collecting surface of the pointer condences the light coming from the light source onto the reflecting member, the light leaking out from the reflecting surface may be almost eliminated and the transmission efficiency of the light may thereby be enhanced. An indicating instrument according to the present invention is characterized in that the rotating shaft is formed into a cylindrical shape, and a light collecting portion having a light collecting surface which faces the light source and a reflecting surface which couples with the collecting surface is formed at the foot portion of the pointer approximately perpendicular thereto, where the outside diameter of the aforementioned light collecting portion is formed to be approximately equal to the inside diameter of the rotating shaft to be press-fitted into the rotating shaft. As a result, since the light collecting portion is press-fitted into the rotating shaft, all the light may come into the light collecting surface and the light transmission efficiency of the device is further raised. An indicating instrument according to the present invention is still further characterized in that the projecting bottom portion of the light collecting portion abuts one end of the rotating shaft. As a result, a precise right angle between the light collecting portion and the rotating shaft is assured without increasing the portion of the light collecting portion interfering with the rotating shaft. An indicating instrument according to the present invention is characterized in that the outside diameter of at least a part of the light source is formed to be approximately equal to the inside diameter of one of the bearings and is positioned thereby. As a result, the bearing is used as a guide to position the light source so that any interference of the light from the light source with the rotating shaft may be eliminated and adjustment of the light axis of the light source to the light collecting surface of the pointer may be made without extra work. An indicating instrument according to the present invention is characterized in that the light source emits a plurality of colors and a switch is used to change the display color. As a result, the illumination color of the pointer may be changed according to the reading of the pointer. An indicating instrument according to the present invention is still further characterized in that the switch means changes the display light color when the reading is under or over a given value. As a result, the pointer indicates zones divided by a given threshold value. In case of a speedometer, for example, when the threshold value is given as 100 Km/h, the pointer indicates a speed warning. An indicating instrument according to the present invention is characterized in that the foot portion of said light conductive pointer is formed integral with said rotating shaft. An indicating instrument according to the present invention further characterized in that said internal driving unit is a stepping motor. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal crss-section of a first embodiment according to the present invention. Fig. 2 is a longitudinal cross-section of a second embodiment according to the present invention. Fig. 3 is a longitudinal cross-section of a third embodiment according to the presnt invention. Fig. 4 is a longitudinal cross-section of a fourth embodiment accirding to the present invention. Fig. 5 is a longitudinal cross-section of a fifth embodiment according to the present invention. Fig. 6 is an electric circuit diagram of the fifth embodiment according to the present invention. BEST MODE OF CARRYING OUT THE INVENTION The present invention will be described in detail with reference to the appended drawings. Fig. 1 is a longitudinal cross-section illustrating a first embodiment of the present invention which is applied to a speedometer for a vehicle. A base member such as a printed circuit board 1 is housed in a main case (not shown) and an internal driving unit 2 is disposed thereon (front surface). Flat synthetic-resinous cylindrical bearings 4 and 5 extending inward are respectively disposed at upper and lower portions of a case 3. A cylindrical rotating shaft 6 which provides an accomodation space 7 at the center inside the shaft is rotatably carried on the bearings 4 and 5. A lower end of the rotating shaft 6 is supported by a step portion 5a of the bearing 5, and its upper end extends upward through an opening 4a of the bearing 4. The inner accomodation space 7 opens to an upper portion of the printed circuit board 1 through the opening 4a of the bearing 4. The internal driving unit 2 includes the bearings 4 and 5 disposed in the case 3 and a stepping motor having a magnet 3a and other members for a rotor integrally secured to the rotating shaft 6, and turns the pointer by an angle corresponding to the level of the speed signal. A dial plate 8 covers an upper surface of the main case (not shown), and has an opening 8a to pass therethrough an upper end portion of the rotating shaft 6 and a graded scale (not shown) printed on the dial plate 8. The pointer 9 is made of a light conductive material such as acrylic resin and is shaped into a long beam. The foot portion of the pointer 9 is formed into a L-shape which has one end forming a light collecting surface 9a and a slant corner formed opposite the light collecting surface 9a, thereby forming a light reflecting surface 9b. A colored layer 10 is formed on the back of the pointer 9 except the foot portion, on which a cover made of synthetic resin is mounted to cover the foot portion as a member of the pointer 9. The cover 11 has a cylindrical connecting member 11a press-fitted into the upper end of the rotating shaft 6. A light emitting diode 12 used as a light source is disposed in the accomodation space 7 inside the rotating shaft 6. Pin terminals 12a are inserted into respective through holes 1a and secured to the printed circuit board 1. Thus, the upper side of the light emitting diode 12 faces the light collecting surface 9a. The light emitting diode 12 is energized through the pin terminals 12a which are soldered to a conductive pattern (not shown) formed on the back of the printed circuit board 1. The operation of the embodiment is explained next. When a speed signal is given to the internal driving unit 2, the rotating shaft 6 turns by an angle corresponding to the vehicle speed, and the pointer 9 turns together with the rotating shaft 6 to indicate the speed. When the light emitting diode is energized and emits light, the light is received by the light collecting surface 9a of the pointer 9, reflected at the light reflecting surface 9b and guided along the beam to the pointed head. The light is then diffused on the way by the colored layer 10 and illuminates the pointer with red color. In the present embodiment, the rotating shaft 6 is formed into a cylindrical shape to provide the accomodation space 7 therein and the light emitting diode 12 is disposed in the accomodataion space 7 and secured to the printed circuit board 1. Therefore, since the light emitting diode 12 is powered through the conductive pattern of the stationary printed circuit board 1, any special structure for used as a power supply as in the first conventional instrument is not necessary, thus resulting in a simple and axially compact structure. Further, since the rotating shaft 6 is formed into a cylindrial shape to provide the accomodation space 7 therein, any special shaft like an offset shaft as used in the second conventional instrument is not necessary. Still further, since the light emlittiing diode 12 is enclosed by the rotating shaft 6, the light emitted from the light emitting diode 12 does not leak out and is transmitted to the light collecting surface 9a of the pointer, so that the light transmission efficiency of the device is improved, thereby illuminating the pointer more efficiently. Since the stepping motor is employed as part of the internal driving unit 2 to turn the rotating shaft 6, more torque may be obtained than the conventional cross-over coil type unit. Fig. 2 illustrates a second embodiment, in which the same reference numerals are put on portions similar to corresponding positions in the first embodiment, and an explanation will be made with regard to different portions. A synthetic resinous bearing 13 which has a step portion 13a and an opening 13b is disposed at the lower portion of the case 3 of the internal driving unit 2. The bearing 13 protrudes upward further than the bearing 5 of the first embodiment. A rotating shaft 14 extending downward is integrally formed at the foot portion of the pointer 9. The upper portion of the rotating shaft 14 is carried by the bearing 4, and the lower portion thereof is supported by a step portion 13a of the bearing 13. The rotating shaft 14 has therein a circular recess 14a opening downward and forms together with the opening 13a of the bearing 13 an accomodation space 15 open to the printed circuit board 1 at the center of the rotating shaft 14. Thus, the top portion of the recess 14a of the rotating shaft 14 forms the light collecting surface 9c of the pointer 9. The light emitting diode 12 is disposed in the accomodation space 15 formed by the bearing 13 and the rotating shaft 14, and is secured to the printed circuit board 1 in the same manner as the first embodiment. Accordingly, the second embodiment also attains the same result as the first embodiment and has a reduced parts count in comparison with the first embodiment. Fig. 3 illustrates a third embodiment, in which the same reference numerals are put on portions similar to corresponding portions in Fig. 2, and an explanation will be made with regard to different portions. A synthetic resinous bearing 16 having a step portion 16a and an opening 16b which forms the accomodation space is disposed at the lower portion of the case 3 of the internal driving unit 2. The bearing 16 protrudes upward much further than the bearing 13 shown in Fig. 2. A solid rotating shaft 17 extending downward is integrally formed at the foot portion of the pointer 9, carried by the bearing 4 at its upper portion and supported by the step portion 16a of the bearing 16 at its bottom portion. The light emitting diode 12 is located in the accomodation space formed inside the opening 16 and secured to the printed circuit board 1 in the same manner as the first embodiment. Thus, the third embdiment also attains the same effect as the second embodiment. Fig. 4 illustrates a forth embodiment, in which the same reference numerals are put on portions similar to corresponding portions shown in Fig. 1, and an explanation will be made with regard to different portions. A synthetic resinous bearing 18 having a step portioon 18a and an opening 18b is disposed at the lower portion of the case 3 of the iinternal driving unit 2. The bearing 18 extends upward further than the bearing 5 shown in Fig. 1 and supports the lower end portion of the rotating shaft 6 at its step portion 18a. The inner surface of the rotating shaft 6 and the lower portion of the opening 18b of the bearing 18 jointly form the accomodation space 19 which is located at the center of the rotating shaft 6 and opens to the printed circuit board 1. A light emitting dioded 20 used as the light source has a base member 20a with its outside diameter greater than the rest and pin terminals 20b and 20b extending from the base member 20a. The outer diameter of the base member 20a of the light emitting diode 20 is formed to be approximately equal to the inside diameter of the bearing 18 or that of the opening 18b so taht the base member 20a is fitted into the opening 18b of the bearing 18 in the accomodation space 19 with the pin terminals 20b and 20b being inserted in the through holes 1a. A flat columnar light collecting portion 21 is integrally formed at the foot portion of the pointer 9 perpendicularly thereto and formed at its lower end surface with a light collecting surface 21a which is convex toward the bottom. A V-shaped cut portion 21b is formed as an inclined reflecting surface 21c at a portion to which the light collecting surface 21a of the light collecting portion 21 couples optically. The outside of the light collecting portion 21a of the pointer 21 is arranged to have approximately the same diameter as the inside of the rotating shaft 6, and the light collecting portion 21 of the pointer 9 is press-fitted into the rotating shaft 6 so that the pointer rotates along with the rotating shaft 6. In this case, the step portion 21d of the light collecting portion 21 abuts the upper end of the rotating shaft 6. When the light emitting diode 20 is energized and emits light 22, the light 22 is received by the light collecteing surface 21a of the light collecting portion 21 of the pointer 9, collected or condensed on the reflecting surface 21c, reflected by the reflecting surface 21c, guided along the pointer 9 to the pointed head and diffused by the colored layer 10 on its way. According to the fourth embodiment stated above, since the curved light collecting surface 21a of the pointer 9 collects or condenses the light 22 coming from the light emitting diode 20, the light is effectively prevented from leaking from the reflecting surface 21 so that the light transmission efficiency at the device may be further improved. Moreover, since the step portion 21d of the light collecting portion 21 of the pointer 9 is arranged to abut the upper end of the rotating shaft 6, an accurate right angle of the pointer 9 to the rotating shaft 6 is assured without increasing portion of the light collecting portion 21 interefering with the rotating shaft 6. Since the outside base portion 20a of the light emitting diode 20 is arranged to have an approximately the same diameter as the inside diameter of the bearing 18 (inside diameter of the opening 18b), the light emitting diode 20 may be positioned by the bearing 18. In other words, the bearing 18 is used as a guide to position the light emitting diode 20 so that an interference of the light emitting diode 20 with the rotating shaft 6 may be eliminated and additional work to align the optical axis of the light emitting diode 20 with the light collecting surface 21a may be avoided. Figs. 5 and 6 illustrate a fifth embodiment of the present invention, in which the same reference numerals are put on portions similar to corresponding portions shown in Fig. 4, and an explanation will be made with regard to different portions. A light emitting diode 23 used as the light source, as shown in Fig. 5, includes a base portion 23a which has the same structure and functions in the same manner as the base portion 20a of the light emitting diode 20, and three pin terminals 23b which extend from the base portion 23a and are inserted into three through holes 1a of the printed circuit board 1. The light emitting diode 23 includes therein two chips emitting differently-colored lights, such as a chip 23c which emits green light and another chip 23d which emits red light. The chips 23c and 23d have their cathodes jointly grounded and their anodes connected through respective swithches 24 and 25, as shown in Fig. 6, to the positive terminal of a battery 26, the negative terminal of which is grounded. In this case, the switch 24 is closed when the reading of the pointer is under a given value, e.g. 100 Km/h, and the switch 25 is closed when the reading of the pointer becomes same as or over 100 Km/h. A reflective layer 27 covers the back surface of the pointer 9, instead of the colored layer 10 in the preceding embodiments. When a speed signal is applied to the internal driving unit 2, the rotating shaft 6 turns by an angle corresponding to the speed signal and, consequently, the pointer 9 turns along with the rotating shaft 6 to indicate the speed. When the reading of the pointer is under 100 Km/h, the switch 24 is closed and the chip 23c for the light emitting diode 23 is energized to emit green light. The light emitted by the chip 23c is received by the light collecting surface 21a of the poointer 9, reflected by the light reflecting surface 21c, guided toward the pointed head and diffused by the reflective layer 27 on its way, so that the pointer is iluminated with green light emitted by the chip 23c. When the reading of the pointer exceeds 100 Km/h, the switch 25 is turned on to energize the chip 23d of the light emitting diode 23, and red light is emitted. As a result, the pointer 9 is illuminated with red light emitted by the chip 23d. According to the fifth embodiment, the same effect as the forth embodiment may be attained and, in addition, the illumination color may be changed according to the reading of the pointer 9. Since the pointer is illuminated with green light when the reading is under a threshold value of 100 Km/h and illuminated with red light when the reading becomes equal or exceeds 100 Km/h, the pointer may be used as a warning signal. INDUSTRIAL APPLICABILITY An indicating instrument according to the present invention is useful as the speedometer for a vehicle, and the structure having a light source emitting different colored lights is especially useful as the indicating instrument for a vehicle.

Claims: An indicating instrument comprising: an internal driving unit (2) including a bearing (4, 5, 13, 16, 18) secured to a base member (1), a rotating shaft (6, 14, 17) carried by said bearing (4, 5, 13, 16, 18) and rotated by said internal driving unit (2), a light conductive pointer (9) disposed to be rotatable along with said rotating shaft (6, 14, 17), and a light source (12, 20, 23) fastened to said base member (1) for illuminating said pointer (9), characterized in that an accomodation space (7, 15, 16b, 19) is formed at the center of said rotating shaft (6, 14, 17) inside at least one of or both said bearing (5, 13, 16, 18) and said rotating shaft (6, 14, 17) to face said base member (1), and said light source (12, 20, 23) is disposed in said accomodation space (7, 15, 16b, 19). An indication instrument according to claim 1, wherein a light collecting portion (21) having a light collecting surface (21a) which faces said light source (20) and a reflecting surface (21c) which couples to said collecting surface (21a) is formed at a foot portion of said pointer (9) approximately perpendicular to said foot portion, and said collecting surface (21a) is formed in a curved shape to condense the light onto said reflecting surface (21c). An indicating instrument according to claim 1, wherein said rotating shaft (6) is formed into a cylindrical shape, a light collecting portion (21) having a light collecting surface (21a) which faces said light source (20) and a reflecting surface (21c) which couples to said light collecting surface (21a) is formed at a foot portion of said pointer (9) approximately perpendicular to said foot portion, and the outside diameter of said light collecting portion (21) is formed to be approximately equal to the inside diameter of said rotating shaft (6) to be press-fitted into said rotating shaft (6). An indicating instrument according to claim 3, wherein a projecting bottom portion (21d) of said light collecting portion (21) of said pointer (9) abuts on one end of said rotating shaft (6). An indication instrument according to claim 1, wherein the outside diameter of at least a part (20, 23) of said light source (20, 23) is formed to be approximately equal to the inside diameter of the bearing (18) and positioned by said bearing (18). An indicating instrument according to claim 1, wherein said light source (23) emits a plurality of colored lights, and switch means (24, 25) is disposed to change one of said colored lights to another. An indicating instrument according to claim 6, wherein said switch means (24, 25) changes one of the colored lights to another when the reading is under, equal to or over a given value. An indicating instrument in accordance with claim 1 or 2, wherein the foot portion of said light conductive pointer (9) is formed integral with said rotating shaft (14, 17). An indicating instrument according to one of the claims 1 to 8, wherein said internal driving unit (2) is a stepping motor.

Inventors: HASHIMOTO HIROSHI, KATAOKA MASAMI, HASHIMOTO, HIROSHI, KATAOKA, MASAMI
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1994
Main classification: G01D11
IPC codes: G01P1, G01D11, G01D13